GWS P51, Zero or Spit - which is best??
10-13-2006, 11:44 PM
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GWS P51, Zero or Spit - which is best??
My 14yo son is ready to move from the EStarter to a low wing & is interested in one of the GWS warbirds. I have a Corsair & he is looking at one of the others. Is there any general consensus as to which one to go for??
(I have a spare E-Flight Park 370 with 2S Lipo to power it. Anysuggestions for props??)
(I have a spare E-Flight Park 370 with 2S Lipo to power it. Anysuggestions for props??)
10-14-2006, 08:13 AM
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RE: GWS P51, Zero or Spit - which is best??
Hi Brett, most of the pilots I fly with like the "Corsair" best, I'm told it's the easiest to fly "stock". By that I mean stock "build", no major airframe mods, but most have a upgraded to a brushless motor and LiPos. Here's a link from Wattflyer about this same question; http://www.wattflyer.com/forums/showthread.php?t=143
If you (or your son) are willing to do a couple of modifications the GWS "Zero" flys as well and will roll and turn a bit faster. The 2 major changes are to decrease the wing incidence by 3/32" to 1/8" and carve out the battery compartment so the battery will slide almost to the firewall, as far forward as you can get it. This is because the "Zero" has a fairly short nose and can be hard to balance with light motors and batteries.
The wing incidence problem (and solution) has been widely covered on e-flight sites, I'll just give a brief description of the "mod". After gluing the fuselage halves together, mark on the wing bolt mounting area a line 1/8" above the existing position. In other words you're raising the trailing edge location "up" 1/8 inch. The leading edge location stays the same. Next, tightly wrap the center section of the wing (top surface) with 200 grit sandpaper and use it as a shaped sanding block to remove material from the wing saddle, be careful to only raise the trailing edge, again the leading edge position remains the same. Since you're also removing foam from the wing fillets it takes a while but eventually you'll reach the line on the bolt mount. Also, because of the dihedral, you'll need to "angle" each side a bit. At this point the wing should be level with the stabilizer, 0 degrees incidence. Reinforce what's left of the bolt mount with F/G tape, it will be very thin now. Last, re-shape the bottom fuselage material behind the wing to match the new position of the trailing edge.That's it!
Good Luck!
Ron
If you (or your son) are willing to do a couple of modifications the GWS "Zero" flys as well and will roll and turn a bit faster. The 2 major changes are to decrease the wing incidence by 3/32" to 1/8" and carve out the battery compartment so the battery will slide almost to the firewall, as far forward as you can get it. This is because the "Zero" has a fairly short nose and can be hard to balance with light motors and batteries.
The wing incidence problem (and solution) has been widely covered on e-flight sites, I'll just give a brief description of the "mod". After gluing the fuselage halves together, mark on the wing bolt mounting area a line 1/8" above the existing position. In other words you're raising the trailing edge location "up" 1/8 inch. The leading edge location stays the same. Next, tightly wrap the center section of the wing (top surface) with 200 grit sandpaper and use it as a shaped sanding block to remove material from the wing saddle, be careful to only raise the trailing edge, again the leading edge position remains the same. Since you're also removing foam from the wing fillets it takes a while but eventually you'll reach the line on the bolt mount. Also, because of the dihedral, you'll need to "angle" each side a bit. At this point the wing should be level with the stabilizer, 0 degrees incidence. Reinforce what's left of the bolt mount with F/G tape, it will be very thin now. Last, re-shape the bottom fuselage material behind the wing to match the new position of the trailing edge.That's it!
Good Luck!
Ron
10-14-2006, 10:44 AM
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RE: GWS P51, Zero or Spit - which is best??
I have the Zero, and have flown the Mustang and Spitfire...
They all fly well, mainly depending on how you set them up...but I like the Spitfire best of those 3...
I agree w/ Ron about the Zero's wing incidence...and I think I will do that to mine (raise the T.E.)
I have an E-Flite park 370-4100kv and 20A. esc and 1320 3 cell TP in it now (started w/ the stock power set-up and 8 cell NiMh ) and it has lots of power
We leave the landing gear off of our planes, because it just adds wt. and causes too much drag IMO...they fly sooo much better w/o the gear...and the Spit lands the best out of these 3 without the gear cuz there's less things underneath to grab the grass...
Make sure you balance 'em a little ahead of the rec. point too...the c.g. "problem" is well doccumented...
They all fly well, mainly depending on how you set them up...but I like the Spitfire best of those 3...
I agree w/ Ron about the Zero's wing incidence...and I think I will do that to mine (raise the T.E.)
I have an E-Flite park 370-4100kv and 20A. esc and 1320 3 cell TP in it now (started w/ the stock power set-up and 8 cell NiMh ) and it has lots of power
We leave the landing gear off of our planes, because it just adds wt. and causes too much drag IMO...they fly sooo much better w/o the gear...and the Spit lands the best out of these 3 without the gear cuz there's less things underneath to grab the grass...
Make sure you balance 'em a little ahead of the rec. point too...the c.g. "problem" is well doccumented...
10-14-2006, 06:01 PM
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RE: GWS P51, Zero or Spit - which is best??
Thanks very much for the comprehensive feedback and the link Ron.... You certainly sound like you've had more than just a little bit of experience in RC! I assume that the wing incidence mod makes the zero stay in trim at varoius throttle settings? This mod must also make the zero require less down elevator when inverted & make rolls more axial? I would imagine you need to use the F/G very sparingly to avoid not adversely affecting the CG.
Thanks too, proptop. How do you reckon the Park 370 would go with 2S Lipos? I've got a 1500 & 2100mah from my Estarter the young bloke can use if they will have enough juice. I thought a 9 or 10x4.7 APC might go OK with it. Do you use an E or SF prop on your 370??
Thanks too, proptop. How do you reckon the Park 370 would go with 2S Lipos? I've got a 1500 & 2100mah from my Estarter the young bloke can use if they will have enough juice. I thought a 9 or 10x4.7 APC might go OK with it. Do you use an E or SF prop on your 370??
10-14-2006, 06:52 PM
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RE: GWS P51, Zero or Spit - which is best??
Hi Brett...
I recon the 2 cell would probably have about as much power as the stock brushed motor with 6-7 cells...in other words, not much.
Maybe with a 10X7sf perhaps? Just a guess there...
If you have a Wattmeter, you could dial it in I'll bet though
My Zero flys with a bunch of down elev. trim, so yes, the wing saddle mod is a good idea...and I've thought of doing it, but this is the first time I've actually read of someone else doing it. (I haven't flown my Zero at all yet this year, but I think I will now )
I recon the 2 cell would probably have about as much power as the stock brushed motor with 6-7 cells...in other words, not much.
Maybe with a 10X7sf perhaps? Just a guess there...
If you have a Wattmeter, you could dial it in I'll bet though
My Zero flys with a bunch of down elev. trim, so yes, the wing saddle mod is a good idea...and I've thought of doing it, but this is the first time I've actually read of someone else doing it. (I haven't flown my Zero at all yet this year, but I think I will now )
10-15-2006, 01:13 AM
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RE: GWS P51, Zero or Spit - which is best??
Hello Brett and Proptop, yes the wing mod reduces the down elevator trim required, 1 or 2 clicks were all I needed for "cruise" speed to remain level. The inverted was smooth also, although not completely "hands off". The wing airfoil, like most of the GWS Warbirds, has a bit of undercamber and still tries to "tuck" towards the top of the aircraft. This is most noticable when more power is applied.
As far as making the rolls more axial, aileron differential is the solution; The torque rod "arms" (the vertical part) should be bent rearward about 30 degrees to provide more "up" than "down" with the same servo throw. This can also be done by using an offset servo arm pivot location (like a wheel) but the wheels I've seen aren't wide enough to drive the ailerons to the necessary total deflection. The longest "straight" servo arm with angled torque rods is easier. Of course, the best solution would be 2 aileron servos with a mixer, but that's a whole different story!
Brett, you're right about the 'glassing adding weight, it builds up fast! Just a strip as wide as the bolt block and a bit longer to tie the block into the remaining fuselage foam is plenty. After the wing saddle shaping, I put the nut and nut plate in place, a drop of oil on the bolt, ran the bolt into place and cut a small hole into the piece of F/G cloth; This allowed the F'/G to slip over the bolt head. Next, slow-drying epoxy over the cloth, and I kept running the bolt in-and-out to keep it from becoming a permanent fixture! Once the epoxy had "gone off" I removed the bolt. On balsa models you can use a heat gun to speed things up but with foam this is not an option.
To Proptop, once the torque rods are in place it is more difficult to use the wing as a sanding block; It can be done but the "throw" (the side-to-side sanding motion) will be shorter. It may be easier to "shave" the wing saddle with a sharp blade and/or a round block. I've used (on other aircraft) a varity of dowels from 2" diameter down to 1/4" diameter, wrapped and glued with 200 grit sandpaper. Take a lot of trial-and-fit but it is worth it!
Good Luck!
Ron
As far as making the rolls more axial, aileron differential is the solution; The torque rod "arms" (the vertical part) should be bent rearward about 30 degrees to provide more "up" than "down" with the same servo throw. This can also be done by using an offset servo arm pivot location (like a wheel) but the wheels I've seen aren't wide enough to drive the ailerons to the necessary total deflection. The longest "straight" servo arm with angled torque rods is easier. Of course, the best solution would be 2 aileron servos with a mixer, but that's a whole different story!
Brett, you're right about the 'glassing adding weight, it builds up fast! Just a strip as wide as the bolt block and a bit longer to tie the block into the remaining fuselage foam is plenty. After the wing saddle shaping, I put the nut and nut plate in place, a drop of oil on the bolt, ran the bolt into place and cut a small hole into the piece of F/G cloth; This allowed the F'/G to slip over the bolt head. Next, slow-drying epoxy over the cloth, and I kept running the bolt in-and-out to keep it from becoming a permanent fixture! Once the epoxy had "gone off" I removed the bolt. On balsa models you can use a heat gun to speed things up but with foam this is not an option.
To Proptop, once the torque rods are in place it is more difficult to use the wing as a sanding block; It can be done but the "throw" (the side-to-side sanding motion) will be shorter. It may be easier to "shave" the wing saddle with a sharp blade and/or a round block. I've used (on other aircraft) a varity of dowels from 2" diameter down to 1/4" diameter, wrapped and glued with 200 grit sandpaper. Take a lot of trial-and-fit but it is worth it!
Good Luck!
Ron
10-15-2006, 03:39 AM
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RE: GWS P51, Zero or Spit - which is best??
Sorry Ron, just to clarify re: axial rolls. ...... you're saying that when in a turn (roll), the aileron deflecting up should be more of an angle than the other side is deflecting down?? I can see how bending the torque rod arms rearward on a single servo set up will achieve that.
Do you have a suggestion how to achieve the same thing with a wing mounted servo setup such as in the F4U mod? Is that what you're referring to when you mention a mixer?
Do you have a suggestion how to achieve the same thing with a wing mounted servo setup such as in the F4U mod? Is that what you're referring to when you mention a mixer?
10-15-2006, 04:26 AM
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RE: GWS P51, Zero or Spit - which is best??
Hi Brett, yes, the up-moving aileron should have more deflection than the downward-moving one for more axial rolls. This is because the airflow over a lifting (non-symmetrical) wing airfoil has already detached on the top surface before it gets to the trailing edge and the ailerons are not as effective on the upper surface. The lower airflow still has pressure (lift, actually) and downward moving surfaces create a much stronger and effective force. The ratio of differential is a matter of ongoing debate, but most agree 2:1 is the highest effective ratio and (about) 3:2 works well on most small models. It does also depend on the exact profile and airspeed, aileron size and shape.
With a 2-servo wing you have many more options. Depending on whether the servo is mounted on the top or bottom surface the servo control arm can be mounted swept forward or rearward, the angle is only limited by the number of splines on the top (crown) gear. For example, with bottom-mounted servos, a 45 degree forward sweep (with controls and trims in netural) would generate a 2:1 up-to-down ratio. Another mechanical adjustment is to use swept or offset control horns on the aileron itself.
A mixer can do this electronically rather than mechanically. Depending on your radio and receiver, the aileron leads will plug into (usually) the main aileron servo port (one lead) and the other lead into an "aux" port, or the "extra" channel many RXs have. Then the transmitter is programmed to "Mix" (combine to a single control actuation) the 2 numbered channels, whatever numbers the two leads are inserted into, and futher mixed to provide differential.
Without a mixer, the mechanical option works fine, just sweep both servo control arms the same amount and connect each to a "Y" connector lead, then plug this into the (single) aileron control port.
Hope this is clear, it's harder to explain than it is to do!
Ron
With a 2-servo wing you have many more options. Depending on whether the servo is mounted on the top or bottom surface the servo control arm can be mounted swept forward or rearward, the angle is only limited by the number of splines on the top (crown) gear. For example, with bottom-mounted servos, a 45 degree forward sweep (with controls and trims in netural) would generate a 2:1 up-to-down ratio. Another mechanical adjustment is to use swept or offset control horns on the aileron itself.
A mixer can do this electronically rather than mechanically. Depending on your radio and receiver, the aileron leads will plug into (usually) the main aileron servo port (one lead) and the other lead into an "aux" port, or the "extra" channel many RXs have. Then the transmitter is programmed to "Mix" (combine to a single control actuation) the 2 numbered channels, whatever numbers the two leads are inserted into, and futher mixed to provide differential.
Without a mixer, the mechanical option works fine, just sweep both servo control arms the same amount and connect each to a "Y" connector lead, then plug this into the (single) aileron control port.
Hope this is clear, it's harder to explain than it is to do!
Ron
10-15-2006, 05:08 AM
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RE: GWS P51, Zero or Spit - which is best??
Great stuff Ron, I'll fiddle around with the angles on the control arms on the (undermounted) servos on the F4U & see how it goes. I don't have a programmable TX so that's my only option.
I've always watched with envy the quick axial rolls in clips as the models exit a low flyby and climbout and wondered how they do it while adding in down elevator so close to the ground. It's a great looking manoeuvre. I've got the F4U to a point where it only needs a little down elevator during rolls, but this may well make the difference. I'll try it at altitude of course.
Thanks also for all the tips on the Zero. The young bloke's been following the thread & seems to be leaning towards the zero over the others, especially when he read that it rolls & turns better than the old man's plane. Teenagers always need to think they know & can do better! The only thing is that he won't be happy with the 2S Lipos & will want (me) to spend more money on 3S batteries. Such is life.....
cheers
Brett
Proptop..... get your Zero out of mothballs & get into it! Good luck!
I've always watched with envy the quick axial rolls in clips as the models exit a low flyby and climbout and wondered how they do it while adding in down elevator so close to the ground. It's a great looking manoeuvre. I've got the F4U to a point where it only needs a little down elevator during rolls, but this may well make the difference. I'll try it at altitude of course.
Thanks also for all the tips on the Zero. The young bloke's been following the thread & seems to be leaning towards the zero over the others, especially when he read that it rolls & turns better than the old man's plane. Teenagers always need to think they know & can do better! The only thing is that he won't be happy with the 2S Lipos & will want (me) to spend more money on 3S batteries. Such is life.....
cheers
Brett
Proptop..... get your Zero out of mothballs & get into it! Good luck!
10-15-2006, 05:49 AM
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RE: GWS P51, Zero or Spit - which is best??
Hi Brett, with the Corsair a sweep of about 30 degrees forward should smooth out the rolls quite a bit. You'll still need a bit of "down" through the middle of the roll since the wing airfoil still wants to lift towards the "top" of the aircraft, even though it's inverted! Just not as much. The main thing you'll notice is a reduced tendency to "Barrel" or widen the circumference of the roll.
I hope your son decides on the Zero, it's really a beautifully-designed aircraft and a great match for the Corsair. When I brought my Zero out to the club field the first time the (many) Corsairs couldn't wait to chase me! "Hey, wait until I trim it!" "No Way!" etc. Lots of fun and laughs.
Good Luck to you both, and yes, those 3s LiPos are a lot faster!
Ron
I hope your son decides on the Zero, it's really a beautifully-designed aircraft and a great match for the Corsair. When I brought my Zero out to the club field the first time the (many) Corsairs couldn't wait to chase me! "Hey, wait until I trim it!" "No Way!" etc. Lots of fun and laughs.
Good Luck to you both, and yes, those 3s LiPos are a lot faster!
Ron
